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Assessing the impact of road developments on connectivity across multiple scales: Application to Yunnan snub-nosed monkey conservation

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... Applications include for example the provision of operational recommendations for prioritization in spatial planning (e.g. Saura, Vogt, Velázquez, Hernando, & Tejera, 2011), prioritizing possible actions for improving the potential functionality of connectivity networks (Clauzel, Xiqing, Gongsheng, Giraudoux, & Li, 2015;Clauzel, Bannwarth, & Foltete, 2015;Zetterberg, Mörtberg, & Balfors, 2010), or advices for the implementation of mitigation strategies (Bergès et al., 2020;Tarabon, Bergès, Dutoit, & Isselin-Nondedeu, 2019). Landscape graphs also permit the comparative assessment of potential impacts of different planning scenarios, such as transport infrastructure developments (e.g. ...
... For modelling movements' paths, we used least-cost distances by characterizing the capacity of each land-cover category to facilitate or impede species movements. The values of resistance to movement were defined using a logarithmic scale following Clauzel, Xiqing, et al. (2015), Clauzel, Bannwarth, et al. (2015). The selected species were then arranged into 16 ecoprofiles in the same way as Mimet, Clauzel, and Foltête (2016) and Sahraoui et al. (2017), not by selecting a species composing each group and serving as ecoprofile but by averaging values of dispersal capacities and movement costs among species composing each group (see Appendix C, Supplementary figure 1 for an example movement costs representation). ...
... In order to avoid connectivity losses as for utopian and transformative scenarios, it should however be accompanied by additional graph-based analyzes for guiding ecological restoration operations. This would consist in determining the most relevant sites for the reconnection of landscape graphs as proposed by Clauzel, Xiqing, et al. (2015), Clauzel, Bannwarth, et al. (2015) and Tarabon et al. (2019) while meeting the challenges of a multi-species approach. ...
Article
This research aims at integrating ecological networks modelling in a participatory approach in order to assess impacts of land-use planning scenarios on landscape connectivity. This approach was applied to the metropolitan area of Bordeaux, a highly dynamic territory that has been modified by several decades of rapid urbanization. Whilst ecological network modelling is widely used in the academic spheres, the concept of ecological network itself also rose within operational stakeholders acting in land-use planning. However, exchanges between scientists and stakeholders about this concept and its modelling and decision-making applications remain rare and generally relate to discussions about results of analyzes carried out by scientists on their own. To our knowledge, no studies to date have involved stakeholders throughout the whole modelling process. In this purpose, we developed an adapted companion modelling approach bringing together scientists and stakeholders for co-constructing (1) a multi-species approach based on ecoprofiles, (2) a conceptual model of the territory’s social-ecological functioning and (3) five land-use planning scenarios over a 15-years horizon. In parallel, we used a landscape graphs approach for modelling ecological networks of ecoprofiles, computing local and global connectivity metrics and estimating scenarios’ impacts on multi-species connectivity. The results globally showed negative impacts of dystopian scenarios or anticipated trends in planning on landscape connectivity (from −20.5% to −8.1% on average, respectively), and in a lesser extent positive impacts of utopian or transformative scenarios (+1.5% and 4.5% on average, respectively). Scenarios’ impacts also varied among ecoprofiles, with some ecoprofiles showing similar or antagonistic effects. These results served as a support of debates between stakeholders on the consequences of policy decisions and actions on connectivity, and on the possibilities of translating connectivity modelling in land-use planning and biodiversity conservation in an urban context.
... However, mitigation planning often underestimated the impacts of development projects on landscape connectivity (Bruggeman et al., 2005). Moreover, even when it is considered, landscape connectivity is not assessed sufficiently in advance to be included in a mitigation hierarchy process (Clauzel et al., 2015;Kujala et al., 2015;Li et al., 2017;Underwood, 2011). In theory, the Law for the Recovery of Biodiversity, Nature and Landscapes in France obliges developers to assess the impact of their project at the landscape level, in particular for the offset aspect (article 69): "Compensation measures are implemented as a priority on the damaged site or, in any case, in its vicinity, in order to guarantee its sustainable functions". ...
... Further, the calculation of offset ratios, i.e. the ratio between damaged and compensation areas, even if scaled to include success uncertainty and the delayed emergence of offsetting gains for biodiversity (Kujala et al., 2015), assumes that the location of the impacted or offset sites within the habitat network does not matter. Third, even if linear transportation infrastructure projects, which cross many ecosystems over wide areas, naturally incorporate the landscape context (Clauzel et al., 2015;Loro et al., 2015), the assessment of other local development projects such as storage sheds, power stations and quarries simply follows a "project-by-project" procedure. This application of the mitigation hierarchy ignores the cumulative landscape-scale impacts of several development projects within the same geographic region (Bigard et al., 2017;Kiesecker et al., 2010;Tarabon et al., 2019b). ...
... Populations, communities and ecological processes are more likely to be maintained in landscapes that encompass an interconnected system of habitats than they are in landscapes where natural habitats occur as dispersed isolated fragments (Crooks and Sanjayan, 2006). Because previous work has not explicitly addressed the NNL of biodiversity objective, we advocate for using landscape graphs and the connectivity metric EC in the mitigation hierarchy to address landscape connectivity issues (Clauzel et al., 2015;Girardet et al., 2013;Sahraoui et al., 2017;Santini et al., 2016). ...
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Biodiversity loss is accelerating because of unceasing human activity and land clearing for development projects (urbanisation, transport infrastructure, mining and quarrying …). Environmental policy-makers and managers in different countries worldwide have proposed the mitigation hierarchy to ensure the goal of "no net loss (NNL) of biodiversity" and have included this principle in environmental impact assessment processes. However, spatial configuration is hardly ever taken into account in the mitigation hierarchy even though it would greatly benefit from recent developments in habitat connectivity modelling incorporating landscape graphs. Meanwhile, national , European and international commitments have been made to maintain and restore the connectivity of natural habitats to face habitat loss and fragmentation. Our objective is to revisit the mitigation hierarchy and to suggest a methodological framework for evaluating the environmental impact of development projects, which includes a landscape connectivity perspective. We advocate the use of the landscape connectivity metric equivalent connectivity (EC), which is based on the original concept of "amount of reachable habitat". We also refine the three main levels of the mitigation hierarchy (impact avoidance, reduction and offset) by integrating a landscape connectivity aspect. We applied this landscape connectivity framework to a simple, virtual habitat network composed of 14 patches of varying sizes. The mitigation hierarchy was addressed through graph theory and EC and several scenarios of impact avoidance, reduction and compensation were tested. We present the benefits of a habitat connectivity framework for the mitigation hierarchy, provide practical recommendations to implement this framework and show its use in real case studies that had previously been restricted to one or two steps of the mitigation hierarchy. We insist on the benefits of a habitat connectivity framework for the mitigation hierarchy and for ecological equivalence assessment. In particular, we demonstrate why it is risky to use a standard offset ratio (the ratio between the amount of area negatively impacted and the compensation area) without performing a connectivity analysis that includes the landscape surrounding the zone impacted by the project. We also discuss the limitations of the framework and suggest potential improvements. Lastly, we raise concerns about the need to rethink the strategy for biodiversity protection. Given that wild areas and semi-natural habitats are becoming scarcer, in particular in industrialised countries, we are convinced that the real challenge is to quickly reconsider the current vision of "developing first, then assessing the ecological damage", and instead urgently adopt an upstream protection strategy that would identify and protect the land that must not be lost if we wish to maintain viable species populations and ecological corridors allowing them the mobility necessary to their survival.
... One of the serious consequences which are attributed to the negative effects of human activities is habitat fragmentation for wildlife. Habitat fragmentation is a spatial process which affect (or potential) core habitats by decreasing their size or increasing their number and/or their isolation of wildlife (Clauzel et al., 2015). Habitat fragmentation of the YSMs is also quite serious due to intensive human activities (such as logging, grazing, mining, agriculture, firewood collecting and other livelihood activities of local people), (Su et al., 2015;Wang et al., 2011;Huang et al., 2017). ...
... Therefore, it is useful to identify the PPAs and restore protection network of the YSMs to enhance the protection efficiency and to balance wildlife protection and its cost in the future (Su et al., 2015;. Protection network of wildlife is crucial for many ecological processes that occur across different spatial and temporal scales, from intra-generational scale foraging to inter-population scale dispersal (Fahrig, 2003;Clauzel et al., 2015). An increasingly popular way of improving and restoring protection network is to model the PCHs and PCCs of wildlife using graph theory which is a set of (potential) core habitats of a given species (called "nodes") potentially connected by functional relationships (or connectivity corridors) (called "links") (Clauzel et al., 2015;Galpern et al., 2011). ...
... Protection network of wildlife is crucial for many ecological processes that occur across different spatial and temporal scales, from intra-generational scale foraging to inter-population scale dispersal (Fahrig, 2003;Clauzel et al., 2015). An increasingly popular way of improving and restoring protection network is to model the PCHs and PCCs of wildlife using graph theory which is a set of (potential) core habitats of a given species (called "nodes") potentially connected by functional relationships (or connectivity corridors) (called "links") (Clauzel et al., 2015;Galpern et al., 2011). The results showed that a total of 16 PCHs, 18 PCCs and the five NRs were protection network of the YSMs, which should be protected completely. ...
Article
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In Southwest China, five Nature Reserves (NRs) (Mangkang, Baimaxueshan, Yunling, Habaxueshan, and Yunlongtianchi) play a key role in protecting the endemic and endangered Yunnan snub-nosed monkey (YSM) (Rhinopithecus bieti). However, increasing human activities threaten its habitats and corridors. We used a GIS-based Niche Model to delineate potential core habitats (PCHs) of the YSMs and a Linkage Mapper corridor simulation tool to restore potential connectivity corridors (PCCs), and defined five scenarios. A normalized importance value index (NIVI) was established to identify the protection priority areas (PPAs) for the YSMs for five scenarios. The results indicated that locations of the habitats and corridors were different in the five scenarios, thereby influencing the distribution of the PPAs and protection network of the YSMs. The NIVI value of Baimaxueshan nature reserve was 1 in the five scenarios, which implied the maximum importance. There were only 7 PCHs and 16 PCCs (with the longest average length of 223.13 km) which were mainly located around 5 NRs in scenario III. The protection network of the YSMs was composed of 16 PCHs, 18 PCCs, and 5 NRs. Under each scenario, most of the PCHs and the PCCs were located in the south of the study area. The five NRs only covered 2 PPAs of the YSMs. We suggest that the southern part of the study area needs to be strictly protected and human activities should be limited. The area of the five NRs should be expanded to maximize protection of the YSMs in the future.
... Landscape graph analysis is often used to quantify potential connectivity by means of connectivity metrics (Foltête, Clauzel, & Vuidel, 2012), to identify the most important landscape elements (patches or corridors) for preserving connectivity (Baranyi, Saura, Podani, & Jordán, 2011;Bodin & Saura, 2010;Crouzeilles, Lorini, & Grelle, 2013;Erős, Schmera, & Schick, 2011;Jordán, Báldi, Orci, Rácz, & Varga, 2003;Saura & Rubio, 2010) or to test different scenarios to improve connectivity. This last goal can be achieved by increasing the size or the quality of existing habitat patches or corridors (Etienne, 2004) or by creating new habitat patches or corridors through landscape restoration (Benedek, Nagy, Rácz, Jordán, & Varga, 2011;Clauzel, Deng, Wu, Giraudoux, & Li, 2015;García-Feced, Saura, & Elena-Rosselló, 2011;Zetterberg, Mörtberg, & Balfors, 2010;Hodgson et al., 2011;McRae et al., 2012). ...
... Land cover was classified into five categories (Table 1) according to the observed preferences of the Yunnan snub-nosed monkey (Clauzel et al., 2015;Li, Yang, & Xiao, 2007;Li et al., 2006;Wang et al., 2011;Wu, Zhou, Long, Du, & Wei, 2005;Zhang et al., 2016) and rasterized at a resolution of 50 m. The elevational distribution of each land cover type was derived from a 30 m-resolution DEM resampled to 50 m using a bilinear interpolation of the Chinese Geospatial Data Cloud (http://www.gscloud.cn/). ...
... The nodes of the graph were defined following the concept of "metapatches" developed by Zetterberg et al. (2010) and previously used in Clauzel et al. (2015) for the snub-nosed monkey. This concept is based on a life traits, and the functional definition of habitat patches depends on the ecological process being considered (Theobald, 2006). ...
Article
Habitat fragmentation is a threat to biodiversity because it restricts the ability of animals to move. Maintaining landscape connectivity could promote connections between habitat patches, which is extremely important for the preservation of gene flow and population viability. This paper aims to evaluate the landscape connectivity of forest areas as it relates to the conservation of the Yunnan snub-nosed monkey (Rhinopithecus bieti), an emblematic and endemic endangered primate species. Specifically, this study seeks to model ways to improve connectivity via cropland reforestation scenarios which incorporate graph theory and genetic distances. The connectivity improvement assessment is performed at two nested scales. At the regional scale, the aim is to quantitatively assess the gain in connectivity from different reforestation scenarios, in which croplands are replaced by different kinds of forest habitats. At the local scale, the goal is to prioritize and to locate croplands based on the gain in connectivity that they would provide if they were reforested. The results indicate that the four reforestation scenarios have different impacts on connectivity; the fourth scenario, in which reforestation is accomplished with plant species that provide optimal monkey habitat, yields the greatest increase in connectivity (+24% versus less than +2% for the others). Prioritization of the 1482 cropland patches shows that the 10 best patches increase connectivity from 0.04% to 9.1% as the isolation threshold distance increases. This kind of graph theoretic approach appears to be a useful tool for connectivity assessment and the development of conservation measures for species impacted by human activities.
... The main purpose of these methods is to answer practical questions about spatial planning and biological conservation. They are used in particular for determining priorities among areas to be protected or restored (Saura and Pascual-Hortal, 2007), improving connectivity, or reducing the effect of disruptive developments (Clauzel et al., 2015;Foltête et al., 2014). Landscape graphs are widely used to preserve or improve connectivity; here we reverse the approach and attempt to identify vulnerable areas in the grassland network where planning measures or direct actions are likely to be most effective in decreasing regional-level connectivity of grasslands. ...
... Following Zetterberg et al. (2010), meta-patches are defined to represent two scales of movement in a nested structure: (1) the level of daily movements (including foraging for example) between patches; (2) the level of dispersal movements between meta-patches. Meta-patches were recently used by Clauzel et al. (2015) and Blazquez-Cabrera et al. (2014). When computing connectivity metrics on the meta-patch level, the analysis is applied to a set of links of a distance greater than the clustering distance. ...
... Like the initial patches, the resulting metapatches were characterized by their capacity, taken as a proxy for their demographic potential. This indicator can result from the addition of the capacity of each patch included in the metapatch, as in Blazquez-Cabrera et al. (2014) and Clauzel et al. (2015). However, to take account of the degree of connectivity within meta-patches, meta-patch capacity was computed by including the potential interactions between patches, defined as ...
Article
The cyclic spread of montane water vole populations in the grasslands of the Jura plateaus causes severe economic, ecological, and public-health problems. Since this phenomenon cannot be managed by massive use of the anticoagulant rodenticide bromadiolone, the challenge is to limit it by reducing regional-level connectivity through landscaping and agro-environmental interventions such as planting hedgerows, ploughing, and cultivating cereals. We used landscape graphs – a spatial modelling approach based on graph theory – to represent the grassland network and identify key areas for intervention. Several strategies were compared in terms of their capacity to fulfil operational requirements by interchanging patches and meta-patches as nodes of the graph, and least-cost distances and resistance distances to weight links. The combination of meta-patches and resistance distances provides a relevant basis on which to design concrete action to decrease regional-level connectivity of grasslands. The results also indicate that the usual removal method applied to the links of the graph would benefit from data on the statistical distribution of cost values along the shortest paths. More broadly, this suggests the modelling approach should be better matched the actual field interventions if the connectivity analysis is to be operational.
... InVEST-Habitat Quality model [35] was used to evaluate snub monkey's habitat quality based on LULC map from 2018 and biodiversity threat factors including villages, village roads, other non-forestry land, economic forest, cropland, and artificial construction [28,36]. We analyzed the correlation between villages, rural roads, and plots to get maximum distance thresholds of villages and rural roads in ArcGIS 10.6 and R [3,8]. Finally, we scored the parameters related to threat factor weights, suitability, and sensitivity of land use types and obtained threat factor attributes ( Table 5) and sensitivity of land use types to threats (Table 6). ...
... The study area and locations of monkey groups in Yunnan Province (China). The numbers labeling each green area represent the monkey group number(1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). ...
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The habitats of the already endangered Yunnan snub-nosed monkey (Rhinopithecus bieti) are degrading as village economies develop in and around these habitat areas, increasing the depopulation and biodiversity risk of the monkey. The paper aims to show the areas of these monkeys’ high-quality habitats that are at highest risk of degradation by continued village development and hence be the focus of conservation efforts. Our analysis leveraged multiple tools, including primary component analysis, the InVEST Habitat-Quality model, and GIS spatial analysis. We enhanced our analysis by looking at habitat quality as it relates to the habitat suitability for the monkey specifically, instead of general habitat quality. We also focused on the impact of the smallest administrative scale in China—the village. These foci produced a clearer picture of the monkeys’ and villages’ situations, allowing for more targeted discussions on win–win solutions for both the monkeys and the village inhabitants. The results show that the northern habitat for the monkey is currently higher quality than the southern habitat, and correspondingly, the village development in the north is lower than in the south. Hence, we recommend conservation efforts be focused on the northern areas, though we also encourage the southern habitats to be protected from further degradation lest they degrade beyond the point of supporting any monkeys. We encourage developing a strategy that balances ecological protection and economic development in the northern region, a long-term plan for the southern region to reduce human disturbance, increase effective habitat restoration, and improve corridor design.
... The next step was to create a collection of edges. We utilized the resistance surface created for the three scenarios, respectively, to calculate the least-cost distance edges (using cumulative cost along least cost pathways) [32]. The final step was to create a landscape graph using the habitat patches and edges discussed earlier. ...
... However, because snow leopard dispersal events were unknown, a variety of distances by increments of 10 km were investigated to see how sensitive the results were to the distance parameter. To build graphs, the Euclidean distance was transformed to the cumulative cost distance using the following equation: Cumulative Cost Distance = eˆ(intercept + β × log(Euclidean Distance)) [32]. Their rates of variation were then computed and compared. ...
Article
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Human modification and habitat fragmentation have a substantial influence on large carnivores, which need extensive, contiguous habitats to survive in a landscape. The establishment of protected areas is an effective way to offer protection for carnivore populations by buffering them from anthropogenic impacts. In this study, we used MaxEnt to model habitat suitability and to identify conservation gaps for snow leopard (Panthera uncia) in the Qilian Mountains of China, and then assessed the impact of highways/railways and their corridors on habitat connectivity using a graph-based landscape connectivity model. Our results indicated that the study area had 51,137 km2 of potentially suitable habitat for snow leopards and that there were four protection gaps outside of Qilian Mountain National Park. The findings revealed that the investigated highway and railway resulted in a decrease in connectivity at a regional scale, and that corridor development might enhance regional connectivity, which strengthens the capacity of central habitat patches to act as stepping stones and improve connections between western and eastern habitat patches. This study emphasized the need for assessing the impact of highways and railways, as well as their role in corridor development, on species’ connectivity. Based on our results, we provide some detailed recommendations for designing protection action plans for effectively protecting snow leopard habitat and increasing habitat connectivity.
... The impact of roads on wildlife distribution, abundance, and population interconnectedness has also been well studied (Andrews, 1990;Carr et al., 2002;Anderson and Raza, 2010;Clauzel et al., 2015). However, most previous studies have assessed the impact of linear infrastructure on wild animals, and typically show that distribution decreases as road density increases (Eigenbrod et al., 2009;Clauzel et al., 2013Clauzel et al., , 2015. ...
... The impact of roads on wildlife distribution, abundance, and population interconnectedness has also been well studied (Andrews, 1990;Carr et al., 2002;Anderson and Raza, 2010;Clauzel et al., 2015). However, most previous studies have assessed the impact of linear infrastructure on wild animals, and typically show that distribution decreases as road density increases (Eigenbrod et al., 2009;Clauzel et al., 2013Clauzel et al., , 2015. Roads likely act as barrier to wildlife movements (Forman and Deblinger, 2000;Trombulak and Frissell, 2000;Coffin, 2007;Zhu et al., 2011). ...
... In this research, IIC was chosen as one of the most commonly employed indices. Many recent studies use IIC only (Clauzel et al. 2015;Hernandez et al. 2015;Huang et al. 2018;Volk et al. 2018), but connectivity studies targeting large-scale disturbances may be difficult to express with a single index, and this research thus utilized a second index, CCP, which views the data from a different perspective than IIC. IIC focuses on the state of the patch, while CCP focuses on the spread of the network (Clauzel et al. 2017). ...
... Another index, CCP, can express the probability of two patches being connected, and also the ease of encounter between organisms (degree of landscape division) from the state of the network in the landscape (Jaeger 2000). Many recent studies use the single index for qualitative analysis (Clauzel et al. 2015;Hernandez et al. 2015;Huang et al. 2018;Volk et al. 2018). Connectivity studies targeting large-scale disturbances, however, may be difficult to express with a single index, and this research thus opted to use both IIC and CCP. ...
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ContextIn March of 2011 a huge tsunami devastated forest habitats along the coast of Sendai Bay in northeastern Japan. Evaluation and monitoring of the changes in habitat connectivity caused by this disaster are essential for managing the recovery of ecosystems and biodiversity.Objectives This research is designed to clarify changes in habitat connectivity caused by the tsunami, as well as subsequent changes due to the process of recovery and restoration.Methods Forest patch distribution maps were constructed from remote sensing data for 2010, just before the tsunami, 2011, immediately after the tsunami, and 2012 and 2016. A binary connection model was employed to generate forest patch network maps for each of the target years, for connectivity distances of 100 m, 800 m and 2500 m. Also, two quantitative connectivity indices, the Integral Index of Connectivity and Class Coincidence Probability were used to assess the changes in continuity.ResultsThe forest patch network map and quantitative indices analysis both showed that not only had the forest habitats been reduced and fragmented by the tsunami, but that continuity kept declining in the following year. By 2016, however, newly established forest patches connected with extant ones, resulting in a slight recovery in habitat connectivity.Conclusions The network maps allowed clear visualization of changes in connectivity over the study period, and were backed up by quantitative results from the indices. This method is relevant for conservation of species with diverse mobility and habitat continuity needs, and for management and restoration of coastal ecosystems.
... Among all the infrastructures, roads have been found to pose the greatest damage to biodiversity [6]. The damages are numerous, ranging from high death rate arising from animal-vehicle collisions [24], destruction and degradation of biodiversity [25], [26], noise and environmental pollution [27], contamination from runoff [8], obstructions in wildlife migration and movement [28], genetic and pollution isolation [7], and strange species of organisms [29], to a high rate of carbon emission [30]. The fragmentation encountered in habitats owing to infrastructural development, coupled with the obstruction of movement is the main challenge militating against the species of organisms, which leads to restrictions and isolation of the species [26]. ...
... The damages are numerous, ranging from high death rate arising from animal-vehicle collisions [24], destruction and degradation of biodiversity [25], [26], noise and environmental pollution [27], contamination from runoff [8], obstructions in wildlife migration and movement [28], genetic and pollution isolation [7], and strange species of organisms [29], to a high rate of carbon emission [30]. The fragmentation encountered in habitats owing to infrastructural development, coupled with the obstruction of movement is the main challenge militating against the species of organisms, which leads to restrictions and isolation of the species [26]. The impacts sustained tend to linger after the construction of the infrastructures [25]. ...
Article
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The geometric rate of biodiversity loss in developing countries like Nigeria has been identified as a problem of major concern. The loss in biodiversity in modern times is evident in the extinction of many plants and animal species. In developing countries like Nigeria, more attention is given to aesthetics, functionality as well as the cost of proposed projects than the environmental impacts of the projects. During construction and rehabilitation of infrastructural projects, biodiversity is destroyed. Thus, this study was aimed at exploring the various ways by which infrastructural projects affect biodiversity, with a view to proffering ways of its restoration. The negative effects of infrastructural projects on biodiversity can be reduced through Environmental impact Assessment (EIA). This will help in averting the detrimental effects on natural resources. In situations, where natural habitat loss is unavoidable, adequate mitigation measures such as provision of strict protection zones along the proposed projects should be adopted. In order to meet sustainable development goal, EIA should be carried out before projects that may have a negative impact on the environment are constructed.
... Land cover was classified into five categories (Table 1) according to the observed preferences of the Yunnan snub-nosed monkey (Clauzel et al., 2015b;Li et al., 2006;Wang et al., 2011;Wu et al., 2005;Zhang et al., 2016) and rasterized at a resolution of 50 m. The elevational distribution of each land cover type was derived from a 30 m-resolution DEM resampled to 50 m using a bilinear interpolation of the Chinese Geospatial Data Cloud (http://www.gscloud.cn/). ...
... The nodes of the graph were defined following the concept of "metapatches" developed by Zetterberg et al. (2010) and previously used in Clauzel et al. (2015b) for the snub-nosed monkey. This concept is based on a life traits, and the functional definition of habitat patches depends on the ecological process being considered (Theobald, 2006). ...
... Scale should be determined based on target groups and the relevance of impacts of the road project. Ecological processes related to connectivity could operate on daily movements at a local scale (Clauzel et al. 2015) or on migratory movements that occur at a regional or global scale (Fullman et al. 2021). At local and regional scales, there is evidence for road effect zones from 1 to 5 km wide in which reduced population abundance was observed for hundreds of species of birds and mammals, respectively (Benítez-López et al. 2010). ...
Road networks affect ecological connectivity, which has implications across different levels of biological organization. There are compelling reasons and sufficient approaches and tools to mainstream ecological connectivity into environmental impact assessments (EIAs) of road projects. In this letter, we discuss ways of overcoming the existing gaps and obstacles in the consideration of connectivity loss in EIAs and how to improve mitigation. The selection of target species, shifting from single to multispecies approaches, and the evaluation of scale optimization are challenges that need to be overcome. We also discuss that the mitigation hierarchy, no net loss targets, and the principles of adaptive management should be applied to increase the effectiveness of mitigation measures. We propose to increase the cooperation between stakeholders and practitioners to enhance co-production and build capacity to conduct evidence-based EIAs for assessing ecological connectivity. Finally, we identify directions for future research that can contribute to integrating connectivity into EIA practice.
... Many publications have evaluated the impacts of road networks on habitats of rare and endangered species, including the Asian elephant, snow leopard (Panthera uncia), Amur leopard (Panthera pardus orientalis), Amur tiger (or Siberian tiger), North Chinese leopard (Panthera pardus japonensis), Cabot's tragopan (Tragopan caboti), Przewalski's gazelle (Procapra przewalskii), black snub-nosed monkey (Rhinopithecus bieti), crested ibis (Nipponia nippon), sable (Martes zibellina), and giant panda (Ailuropoda melanoleuca) (Zhang et al., 2015;Kang et al., 2015Kang et al., , 2020Liu et al., 2017;Zheng, 2018;Jiang et al., 2014;Celine et al., 2015;Xing et al., 2019; Yang et al., 2012;Xiao et al., 2019). From these studies it could be seen that the snow leopard, Cabot's tragopan, and Przewalski's gazelle are seriously affected by habitat fragmentation (Zhang et al., 2015). ...
Article
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Two strategic documents issued by the Chinese Central Government projected that, by the mid-21st century, the linear transport infrastructure (LTI) network of China will rank at the forefront of ecological and sustainable transport networks globally. With this goal, it is urgent to summarize existing research, benchmark international research levels, and propose development directions and strategies for terrestrial vertebrate species protection around LTI in China. In this study, we searched for peer-reviewed papers before 2020 in both Chinese and international databases. A total of 170 academic articles were collected. Most focused on roads, but some focused on railways, of which the Qinghai-Tibet Railway occupied half. The most researched taxa were mammals, including the Tibetan antelope (Pantholops hodgsonii), Siberian tiger (Panthera tigris), and Asian elephant (Elephas maximus), the number of bird research papers was less than half that of mammal research papers, and fewer amphibian and reptile studies. The impact of LTI on wildlife was classified to habitat effects, roadkill, behavioral influences, and barrier effects. Wildlife preservation efforts included wildlife and habitat surveys, route selection, subgrade and pavement design, and the design and monitoring of wildlife crossing structures. Studies were concentrated in five zoogeographical regions, i.e., the Qinghai-Tibet, South China, Central China, Northeast China, and Southwest China regions. Conservation suggestions, knowledge gaps, and future research directions for China were identified through comparisons with the state of international research. These focal priorities will help guide the development of road ecology in China. Multi-disciplinary, cross-departmental, and national level research is necessary. Based on this review, a national data integration platform should be established and efforts to cooperate with international research teams to mitigate the adverse effects of LTI should be made.
... Therefore, structural connectedness is not necessarily synonymous to functional connectivity (Tischendorf and Fahrig, 2000), and relying solely upon the concept of structural corridors (connectedness) ignores the species' reaction to the landscape structure and heterogeneous environments (connectivity) that affect the distribution of the species (Taylor et al., 2006). (Clauzel et al. 2015;Mimet et al. 2016). The goal of many of these approaches is to improve the environmental relationship in the design of the protection network and increase the reproducibility of connection estimation while reducing subjectivity at all stages. ...
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Maintaining linkages between remaining natural areas is increasingly important to ameliorate the negative effects of habitat loss and fragmentation on wildlife populations. Identifying environmental corridors is critical to biodiversity conservation and landscape planning. In recent decades, many methods have been developed to increase ecological linkages and establish gene binding to prevent mismanagement of protected areas. However, the multiplicity and complexity of methods can be a barrier for conservation planners. Here, we combine a limited set of several methods to provide a connection analysis framework that provides iterative, intuitive, and environmentally related connection estimates. In this study, firstly we investigated the habitat suitability of Armenian Wild sheep as a target species by ecological niche factor analysis. Then, by using the theory of electrical circuits and analysis of the least cost route of habitat communication between habitat spots was investigated. Based on flow maps, movement patterns and functional communication were identified for the target species as well as important communication areas in the study area. The results show that based on the circuit theory approach, the flow through the pixels (nodes) is equivalent to the probability of species movement. Therefore, it can be interpreted that if the target species travel between the mentioned habitats, the sections with high flow intensity will be the most probable route for their passage. Identification of important communication areas in the region is another important result of flow maps. The protection of these important areas is very important.
... Road ecology aims to investigate the impacts of roads on individuals, populations, and communities of wildlife to avoid, minimise, and compensate for the negative impact of roads (van der Ree et al., 2011). The impact of road development on wildlife has been explored for several decades now (Clauzel et al., 2015), and road ecology has described many negative effects of roads on biodiversity but it is still to understand their evolutionary consequences (Brady and Richardson, 2017). For example, populations adapted to living in highly fragmented landscapes may lose their viability when habitat availability becomes too fragmented (Hanski, 2015), leading to local extinctions. ...
Article
Roads negatively affect wildlife populations globally, causing habitat fragmentation that can facilitate mortality by access to forest for poaching and wildlife collisions with vehicles. Primate habitats are vulnerable to fragmentation exposing them to anthropogenic threats. Endangered dusky langurs (Trachypithecus obscurus) in Malaysia are often found in urban areas and have been frequent victims of vehicle collisions. To mitigate the hazardous impact of a busy asphalt road on wild dusky langurs in Teluk Bahang, Penang, we built the first artificial road canopy bridge in Malaysia in February 2019 to assist arboreal wildlife to move between habitat fragments more safely. Four days after the bridge construction, the first long-tailed macaque (Macaca fascicularis) was recorded via a camera trap crossing the bridge, and plantain squirrels (Callosciurus notatus) and dusky langurs first crossed one and eight months later, respectively. The bridge was upgraded from a single-firehose rope to a double-rope in August 2020 to assess the effectiveness of the two designs. In total, 2128 animal crossings comprising three mammal species were recorded between March 2019 and May 2021. Plantain squirrels crossed the bridge most frequently with 2075 crossings, long-tailed macaques crossed 32 times, and dusky langurs 21 times. There was a significant difference in bridge use according to species between the two designs (Chi-Square, p < 0.001). Since the construction of the bridge, the rate of previously frequently reported primate roadkills near the bridge location has dropped to zero. This successful pilot project has spurred the efforts to implement more canopy bridges country-wide to support primate conservation efforts and better protect arboreal wildlife from the negative impacts of linear infrastructure.
... In particular, arboreal species may have serious difficulties in crossing vegetation gaps caused by infrastructures, limiting their access to resources such as food and mating partners, and restructuring populations into smaller and often unviable populations (Ascensão et al. 2019;Grativol et al. 2001;Linden et al. 2020). Some species may avoid infrastructures due to disturbance such as traffic noise and increased human activity (Duarte et al. 2011), thus intensifying this barrier effect (Clauzel et al. 2015;Hickey et al. 2013). In addition, roads, railways, and power lines kill numerous animals due to collisions and electrocution, further depleting populations (Borda-de-Água et al. 2017;Cunneyworth and Duke 2020;Hetman et al. 2019;Katsis et al. 2018). ...
Article
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Approximately 65% of primate species are facing extinction, with threats including the impacts of linear infrastructures such as roads, railways, and power lines, associated with habitat loss and fragmentation, direct and indirect mortality, and changes in animal behavioral patterns. Nevertheless, this is an often-overlooked topic in primatology, and there is limited information on which regions and species are most affected by linear infrastructures. Here, we provide a global assessment of priority areas and primate species for conservation by integrating information from global-scale open-access data sets on the distributional ranges, traits, and threats to primate species and linear infrastructures, together with a systematic literature review and a questionnaire sent to primatological societies. We produced a bivariate map that reflects the patterns of co-occurrence of the Conservation Value and Infrastructure Density. From this map we highlight Primate Mitigation Areas (regions with high Primate Conservation Value and Infrastructure Density), which are areas where infrastructure mitigation should be prioritized; and the Primate Preservation Areas (regions with high Primate Conservation Value and low Infrastructure Density), which represent areas that should be preserved from further infrastructure development. Primate Mitigation Areas primarily include the Atlantic forest of Brazil, the Guinean forests of West Africa, and most of Southeastern Asia, whereas Primate Preservation Areas are found principally in the Amazon and Congo River basins. Our assessment also produced a list of priority species affected by infrastructures, with the great apes and gibbons ranking highest. Global infrastructure projects, especially the Belt and Road Initiative, can seriously affect both priority areas (particularly preservation areas) and the most vulnerable species, due to the massive sprawl of linear infrastructures and associated human activity. Thus, we call for dedicated strategic environmental and social assessments throughout these different economic corridors within the Belt and Road Initiative planning process, prior to developing the different projects. Our assessment can serve as a tool to coordinate management actions and legislation around the world.
... In the field of environmental impact assessment: Where might species be the most impacted by landscape changes [9], climate changes [29][30][31], or natural disasters [32]? Where will the potential ecological impacts caused by the development of transport infrastructures [33][34][35] or of a large urban infrastructure [36] occur? Graphab has also proved useful in many biological conservation studies, primarily to identify the priority locations for maintaining the connectivity level of a habitat network [37][38][39][40][41][42][43]. ...
Article
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Landscape graphs are increasingly used in ecology, conservation, and landscape planning for modeling habitat connectivity of wildlife species. We present here the follow-up of Graphab, a software application for modeling habitat networks. This application has been recently enhanced by advanced functions of spatial analysis, command-line facilities, and connections with other software applications. It has been used in many studies, first in ecological studies for analyzing the role of landscape connectivity on biological responses measured in the field, second for supporting decisions concerning biodiversity preservation. Future improvements could be made to make the links more realistic with respect to ecological processes.
... Habitat connectivity is a function of the area, quality, and configuration of habitat, as well as of the dispersal capability of species (Hodgson et al. 2009), and, hence, is sensitive to spatial variations in habitat, such as habitat loss, degradation, and fragmentation (Clauzel et al. 2015;Inoue and Berg 2017;Lechner et al. 2017). For example, the loss of habitat patches that serve as connectors for other patches can greatly reduce habitat connectivity and has an adverse impact on the abundance, diversity and stability of populations (Thompson et al. 2017;Peeters et al. 2020). ...
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Context Habitat connectivity is essential for the long-term persistence of species, but is commonly disregarded in climate change impact studies. The Tibetan Plateau contains a biome rich in endemic ungulates, which are highly sensitive to climatic variations and deserve particular attention in conservation planning against climate change. Objectives We evaluated the response and vulnerability of habitat connectivity to climate change for four ungulate species endemic to the Tibetan Plateau, and examined the robustness of protected areas (PAs) for the conservation of these species under climate change. Methods For each focal species, we developed ecological niche models to predict the spatial variations in habitat under climate change and conducted a network-theoretical analysis to estimate the consequent changes in habitat connectivity. Moreover, we used the circuit theory to characterize dispersal patterns of these species and conducted gap analyses to estimate the contribution of existing PAs to the conservation of these species. Results The four focal species will experience a remarkable connectivity loss that outpaced their habitat loss in response to climate change. Currently, 53.39 and 46.64% of the areas that could contribute to the habitat suitability and connectivity, respectively, of these species are unprotected. These values could further increase under future climate conditions. Conclusions Climate-driven habitat variations may lead to the loss of key connectivity areas between the habitats of ungulates, causing disproportionate decrease in habitat connectivity. The existing PAs on the Tibetan Plateau are not robust for the conservation of the four ungulates. Adjustment of certain key PAs may help to address the conservation gaps.
... La première étape consiste à fixer les bornes caractérisant les milieux les plus attractifs et perméables et ceux bloquants ou répulsifs. Les valeurs des classes intermédiaires peuvent être définies à partir de fonction de transformation de type exponentielle (par exemple Trainor et al., 2013;Keeley et al., 2016;Duflot et al., 2018), logarithmique (Braaker et al., 2017), sigmoïdale (Moulherat et al., 2020) ou suivant d'autres règles cherchant à dissocier clairement les classes entre elles (Clauzel, Xiqing, et al., 2015;Li et al., 2015;Sahraoui et al., 2017). Bien que les analyses de sensibilité des valeurs de coûts soient encore rares, certains auteurs ont en effet montré que l'écart relatif entre les valeurs est plus important que les valeurs en soient (Chardon et al., 2003;Rayfield et al., 2011). ...
Thesis
La biodiversité est confrontée à une érosion accélérée et est devenue une préoccupation environnementale mondiale ces dernières décennies. En France, la séquence Éviter–Réduire–Compenser (ERC) est un des outils réglementaires mis en place dans un contexte de destruction et de fragmentation des habitats d’espèces. Elle permet le développement des territoires tout en visant une absence de perte nette de biodiversité. Cependant, malgré les récentes évolutions réglementaires européennes et françaises, le triptyque ERC présente de nombreuses limites et enjeux d’ordre opérationnel. En positionnant nos travaux à l’interface entre recherche et opérationnalité, nous proposons un cadre méthodologique basé sur plusieurs approches de modélisation afin d’améliorer les processus d’évaluation et décisionnels aux différentes étapes d’aménagement, de la planification à l’opérationnel au moment de l’autorisation des projets. Dans une première partie du travail, nous intégrons les enjeux spatio-temporels de la biodiversité à l’ensemble de la séquence ERC, de l’évaluation des impacts potentiels au dimensionnement des mesures écologiques. À partir du cas précis de l’aménagement du Grand Stade de Lyon, nous montrons l’intérêt de combiner les modèles de distribution d’espèces et les graphes paysager pour identifier les réseaux écologiques et poser un cadre de calcul de l’équivalence écologique basé sur le volet fonctionnel de la biodiversité. Intégrer les dimensions spatiales et temporelles permet d’accroitre la connectivité des habitats et améliorer la conception des projets. Nous montrons ensuite qu’organiser la compensation à l’échelle des territoires en les intégrant aux réseaux écologiques améliore davantage les bénéfices et réduit le risque d’échecs des mesures. Notre démarche est présentée dans le contexte périurbain de l’Ouest de Lyon. Enfin, nous démontrons les implications d’une démarche anticipée et planifiée de la séquence ERC dans la planification stratégique des territoires. Pour cela, nous montrons dans le cadre de la Métropole de Toulouse l’intérêt d’étudier conjointement les dynamiques urbaines et écologiques pour mettre en place une stratégie de conservation de la biodiversité à l’horizon 2040 en assurant l’absence de perte nette sur les habitats d’espèces et leur connectivité selon différentes trajectoires d’urbanisation et de ratio de compensation. Cette thèse offre une approche globale pour orienter les décideurs et améliorer la prise en compte des fonctionnalités écologiques à différentes échelles spatiales et temporelles dans l’aménagement des territoires et l’application de la séquence ERC. Ce travail est basé sur des logiciels novateurs et accessibles pour tous les acteurs et constitue une contribution intéressante à l’appui des maitres d’ouvrage qui souhaitent s’assurer de l’absence d'effets significatifs ou irréversibles sur la biodiversité, et des autorités environnementales qui veillent à ce que l’ensemble des enjeux environnementaux soient bien pris en compte dans la conception des projets d’aménagement.
... À l'heure actuelle, des politiques visant l'absence de perte nette de biodiversité ont été mises en place dans plus de 80 pays (Maron et al., 2018) et portent sur différentes composantes de la biodiversité (Bezombes et al., 2018 ;Carreras Gamarra et al., 2018). En France, la séquence ERC s'applique en théorie à l'ensemble de la biodiversité, mais n'est mise en place en pratique que lorsque des règlementations spécifiques existent (Regnery et al., 2013) Jusqu'à présent, les évaluations environnementales ont assez mal pris en compte les impacts des projets de développement à l'échelle du paysage (Bruggeman et al., 2005) ou ne sont pas planifiées assez tôt à l'avance pour inclure l'ensemble de la séquence ERC, notamment la phase d'évitement (Underwood, 2011 ;Clauzel et al., 2015 ;Kujala et al., 2015). Pourtant, les travaux de la Commission européenne 4 soulignent l'importance de considérer la connectivité des sites impactés à l'échelle du paysage et plusieurs pays ont intégré la prise en compte des processus écologiques à l'échelle du paysage dans l'application de la séquence ERC (voir l'exemple des Pays-Bas dans l'ouvrage de Wender et al. 2018). ...
Article
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National, European and international commitments have been made to maintain and restore the connectivity of natural habitats to face habitat loss and fragmentation. Meanwhile, environmental policies in different countries worldwide have proposed the mitigation hierarchy to reach the goal of "no net loss (NNL) of biodiversity". The mitigation hierarchy aims at assessing all the ecological impacts of a development project, but the impacts on landscape connectivity are not properly addressed. We propose an operational framework to assess the environmental impacts of a development project on landscape habitat connectivity. This framework is based on graph theory and the equivalent connectivity index EC of "amount of reachable habitat", which takes into account the total amount of habitat, the spatial configuration of habitat patches and the dispersal capacities of the species. We redefine the three main issues of the mitigation hierarchy regarding "no net loss of connectivity". Then, this framework was applied to a simple, virtual network case where several scenarios of impact avoidance, reduction and compensation were tested and compared. We discuss the benefits and limitations of this approach for the mitigation hierarchy and provide practical recommendations for implementation. In conclusion, we advocate and justify a better integration of the three main biodiversity conservation policies in France : the law for the recovery of biodiversity, nature and landscapes, the SRADDET and the strategy for the establishment of protected areas.
... Diversity 2019, 11, 100 2 of 12 that extend into the surrounding landscape [21][22][23]. Restrictions on individual movement such as daily displacement, home range, seasonal migration, or dispersal [24,25] ultimately have negative consequences for population size and persistence [19,26]. Areas free of linear infrastructure are essential for arboreal species in tropical forests [27,28] because these species rely on canopy connectivity to move through the landscape to perform vital activities, e.g., feed, find mates, and reproduce [29]. ...
Article
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Linear infrastructures are a primary driver of economic development. However, they also can negatively affect wildlife by mortality and the barrier effect. In this paper, we address how paved and unpaved roads, high-tension power lines, and gas/oil pipelines affect home range size, core areas, and movement in an endangered primate, the golden lion tamarin (GLT). Location data were recorded using radio telemetry on 16 groups in two protected areas and in privately owned forest fragments. The GLT’s home range, not core area, increased in size for the groups that occupied locations far from linear infrastructures; home range was also significantly influenced by available forest size. None of the home ranges contained a road, but home ranges did contain power lines. GLTs used the surrounding landscape near all types of infrastructure. Movement analysis showed that most of the step lengths (distances between subsequent locations) were less than 100 m between two consecutive locations, but step length was longer for roads and longer for groups in fully forested habitats. Tamarins avoided paved roads when in close proximity to this type of infrastructure; this behavior increased in areas without adequate adjacent forest habitat. Our results show that linear infrastructures differ in their level of impact: roads can act as a barrier, whereas other types of infrastructure have minimal effect on movement and home range. We discuss these differences in impact in terms of structure, maintenance schedules, and edge effects of infrastructure.
... In response, the group size of some R. bieti groups have shown an increase in past years, such as Lasha and Longma groups in southern unit, the group size has increased from 50 to 130 during 1988and 2004, and from 50 to 127 during 1988, respectively (Long et al. 1994, Li et al. 2014, Xu et al. 2015, Huang et al. 2017. However, in the monkeys' southernmost distribution range, the high-quality habitats are currently limited in size, highly fragmented, and disturbed by urbanization, roads, grazing, farmland and firewood collection of local people (Clauzel et al. 2015. Habitat loss and group isolation may prevent gene exchange between groups in the southern unit, making them highly vulnerable to extinction due to environment change (Xiao et al. 2003, Liu et al. 2009). ...
... Nowadays, graph theory has mostly been applied to animal taxa (Bunn et al. 2000;Pascual-Hortal and Saura 2008;Crouzeilles et al. 2015;Clauzel et al. 2015;Fernandes et al. 2015;Segurado et al. 2015;Brodie et al. 2015;Pérez-Hernández et al. 2015;Tittler et al. 2015;Kang et al. 2016;Correa et al. 2016). Whereas in the case of focal species of flora, few studies have addressed landscape connectivity (Aavik et al. 2014;Molina et al. 2015; 1 3 Craven et al. 2016;Correa et al. 2016Correa et al. , 2017a, and thus, the ecological and/or genetic patterns that may be influenced by landscape connectivity have yet to be established. ...
Article
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Fragmentation transforms natural habitats into a set of structurally and functionally differentiated small and separated patches, and causes the loss of connectivity among populations. In this study, we used a multi-temporal approach (1986, 2011 and 2016), to analyze the patterns of habitat fragmentation and to identify critical zones for the maintenance of habitat connectivity of two focal pine species (Pinus pseudostrobus and P. montezumae) with the broadest distribution and highest economic importance in the temperate forests of the Meseta Purépecha, in Michoacán, Mexico. This eco-region is currently one of the most threatened in terms of habitat degradation and extinction of forest communities. From a supervised classification of satellite images, land use coverage classes were selected and used as a basis to analyze the degree of landscape fragmentation using configuration and composition metrics and landscape connectivity based on the graph-theory approach. The fragmentation metrics suggested an increase in agricultural coverage (10.81%; fruits crop, mainly avocado), while the coverage of the forest showed a reduction (15.06%) and fragmentation throughout the study period. The landscape connectivity is lower (16.3% on average) and showed two highly important zones (Uruapan and Tancítaro) and one zone of high importance (Pátzcuaro) to maintain connectivity, considering three different dispersion distances (0.5, 5.0 and 10 km) for the species analyzed. We propose these three zones as potential habitat stepping stones to promote overall landscape connectivity, offering primary habitats and possible ecological resilience for this important forest ecosystem.
... It has been called the Yunnan or black snub-nosed monkey, but since it also occurs in Tibet (Xizang province of mainland China), Yunnan snubnosed monkey seems restrictive. Since R. strykeri, which has an all-black body, was described in 2010, Chinese scholars have been calling it the black snub-nosed monkey (e.g., Chen et al. 2015), and R. bieti the black-and-white snub-nosed monkey (e.g., Clauzel et al. 2015). Black-and-white snub-nosed monkey in Chinese is "Hei Bai Yang Bi Hou," 黑 白 仰 鼻 猴. ...
Article
Rhinopithecus bieti Milne-Edwards, 1897 is 1 of the largest and most northerly colobine monkeys. It lives at the highest recorded elevations for a nonhuman primate, 2,625-4,700 m. It has a restricted range between the Yangtze and Mekong Rivers in Yunnan and Xizang (Tibet) Provinces, mainland of China, in 15-20 groups comprising 6 isolated populations. It lives in multimale- multifemale bands of up to 480 individuals comprising cohesive 1-male units of < 20 individuals in nonoverlapping home ranges. Bands may have 1 or more all-male units. Mating and parturition are seasonal. With a total population of about 3,500, it is 1 of the most endangered primates and is listed as Endangered by the International Union for Conservation of Nature and Natural Resources.
... Many studies are based on such planning scenarios. Clauzel et al. (2015b), Fu et al. (2010), and Vasas et al. (2009) compare several options for the siting of transport infrastructures. From a more theoretical perspective, Tannier et al. (2012) and Tannier et al. (2016) assess the ecological impact of several patterns of residential development, and Huang et al. (2018) compare actual and counterfactual scenarios of urban growth. ...
Article
Ecological networks are tools for conservation planning that rely on the concept of connectivity. Criticisms leveled at them are that they are widely used in a dogmatic way regardless of how they compare against other tools and that their efficiency is rarely assessed. I propose to include landscape graphs in the debate because they are designed to be operational models of ecological networks. I outline the key features of landscape graphs that can be matched with some of these criticisms: weighting of patches and links to take the landscape matrix into account, integrated metrics dealing with both connectivity and amount of habitat, and the possibility of including them in a decision-support system based on scenario analyses. I conclude that criticisms of ecological networks reveal the lack of diffusion of modeling tools such as landscape graphs, and that approaches such as participatory modeling bringing together scientists and practitioners could be one way to improve matters.
... Therefore, we first identified the landscape types that were easiest to modify in terms of configuration to improve their suitability, i.e., the ones that require the slightest configuration changes while keeping the composition similar. Then, we prioritized these landscape types according to the gain in connectivity they provided if their configuration was made more suitable using a patch addition process in Graphab 2.0 (Clauzel, Xiqing, Gongsheng, Giraudoux, & Li, 2015;Foltête et al., 2014;Mimet, Clauzel, & Foltête, 2016). The process began by computing the global PC index that quantified the connectivity of the initial state. ...
Article
https://www.sciencedirect.com/science/article/pii/S0169204618305760 Environmental policies have highlighted the importance of preserving ecological networks to limit the fragmentation of natural habitats and biodiversity loss. A crucial issue for landscape managers is how to reconcile conservation measures that benefit all species and the maintenance of human activities. This study aimed to promote landscape multifunctionality, i.e., improving connectivity for several species without significantly modifying human activities. The objectives were to identify the most strategic natural landscape types to prioritize for preservation and to propose landscape management actions in highly anthropized areas that would benefit a majority of species. The analysis combined landscape types and bird species observation data to model landscape suitability for six species profiles defined by their affinity for wetlands, agricultural areas, urban areas and three types of forested landscapes. By graph modelling, we analysed the functional connectivity of the ecological networks of these species profiles. The results revealed that only ten landscape types out of 72 were core habitats for three species profiles simultaneously. These were primarily forested landscape types — either strict or associated with open areas (wasteland, forest clearing). Conversely, some anthropogenic landscapes dominated by built areas and sometimes shared with agriculture were completely unfavourable for all species profiles. The graph modelling analysis showed that the transformation of some landscape types could potentially improve connectivity for four species profiles presenting different ecological requirements. This coupling approach thus provided guidance to propose some landscape management actions that benefit the majority of species while preserving land uses.
... Specifically, graph-theoretic approaches are commonly used where a network's core areas represent the graph's nodes and its corridors represent edges or links (Fall, Fortin, Manseau, O'Brien, & O'Brien, 2007;Urban & Keitt, 2001). Graph-theoretic approaches have great potential for practical conservation (Zetterberg, Mortberg, Balfors, & Mörtberg, 2010) and have been useful for multi-scale connectivity analyses (Dilts et al., 2016;Tambosi, Martensen, Ribeiro, & Metzger, 2014) or comparing connectivity estimates for different landscape scenarios (Clauzel, Xiqing, Gongsheng, Giraudoux, & Li, 2015;Mimet, Clauzel, & Foltête, 2016). Many of these approaches aim to improve the ecological relevance of conservation network design and to increase repeatability of connectivity estimates, while reducing subjectivity throughout the process. ...
Article
Maintaining connectivity among remaining natural areas has become increasingly important to ameliorate the negative effects of habitat loss and fragmentation on wildlife populations. Early corridor networks were based on structural connectivity (i.e. habitat structure) and designed to connect protected areas. In recent decades, many methods have been developed to increase the ecological realism of such corridor design to avoid misguided management. However, the multitude and complexity of methods can be a hurdle for conservation planners. Here, we combine a limited set of multiple methods to present a connectivity analysis framework that produces repeatable, intuitive, and ecologically relevant connectivity estimates. We use a modified habitat suitability analysis, accounting for protected area effectiveness, as a starting point for least-cost corridor estimates, and evaluate the network using graph theory. We apply the framework to an existing corridor network in Belize, Central America, by estimating potential functional connectivity for white-lipped peccaries Tayassu pecari between systematically identified core patches. We found that forest productivity and protected area effectiveness were important predictors of habitat suitability for white-lipped peccaries. The graph-theoretic network analyses identified particularly important core areas for overall landscape connectivity and indicated potentially weak links in the existing network, while the least-cost corridor outlines indicated general areas where the implementation of connectivity-enhancing measures could strengthen such weak links. With this study, we provide a framework to improve the scientific rigour, ecological meaningfulness, and conservation relevance of applied corridor network design.
... Changes in primate behaviour in response to habitat degradation have been reported in regions undergoing intense fragmentation (Clarke et al. 2002), where individuals can explore forest edges more strictly (Pozo-Montuy & Serio-Silva 2007). For example, in a Chinese region bisected by roads, the black snub-nosed monkey Rhinopithecus bieti (Clauzel et al. 2015) moved daily among foraging areas scattered in the matrix. The clear preference for disturbed fragments and for forest fragment edges in the vicinity of roads and urban areas may be an indication of cross-habitat spillover. ...
Article
There are several primate species with high risk of extinction in small forest fragments disturbed by human activities. However, some species exhibit high ecological plasticity, which allows them to persist in human-modified landscapes. The main goal of this study is to examine the relative roles of vegetation (mean distance among trees and mean canopy cover), human disturbance (distance to the road, distance to the fragment edge and edge type), and habitat spatial configuration (spatial autocorrelation index, category of quadrat – position within the fragment/fragment type) on the habitat selection of the black-tufted marmoset Callithrix penicillata in forest patches. We selected forest patches near and away from roads/urban areas, in southern Minas Gerais state, south-eastern Brazil. We used generalized linear mixed models to explain the presence of black-tufted marmoset in those patches. Our results show that black-tufted marmoset tend to occupy forest fragments closer to roads/urban areas, and consequently are under the influence of anthropic disturbance. In addition to the area delimited by these fragments, there is a preference for edge environments, where disturbances are exacerbated and the ecological conditions are suitable for exploitation by the black-tufted marmoset (supply of gum trees and reduced risk of competition). We suggest that a cross-habitat spillover by marmoset occur from forests to small habitat patches close to human-modified areas, such as those in proximity to roads and urban zones.
... et al. (2010),Gurrutxaga et al. (2011),Gurrutxaga & Saura (2014),Clauzel et al. (2015),Loro et al. (2015),Santini et al. (2016b),Dalloz et al. (2017).Supporting conservation planning for the conservation of endangered or near-threatened species.Ziólkowska et al. (2012), Trainor et al. (2013), Harris et al. (2014), Zhang & Gorelick (2014), Espinoza et al. (2015), Ramirez-Reyes et al. (2016), Ahmadi et al. (2017), Diniz et al. (2017), Dosen et al. (2017), Martinez-Pardo et al. (2017). Evaluating the impacts of climate change, drought scenarios and sea-level rise on species and habitats. ...
... Unless physical and habitat barriers to intergroup or inter-subpopulation migration are eliminated, several species are likely to go extinct in the next 25-50 years (Wong, Li, Xu, & Long, 2013). For example, in the case of the Yunnan black and white snub-nosed monkey, Clauzel, Xiqing, Gongsheng, Giraudoux, and Li (2015) present data that the presence of permanent infrastructure such as roads and buildings prohibits long-distance migration and this has contributed to the isolation of the two northern subpopulations from the remaining three subpopulations inhabiting the Baima Snow Mountain Reserve. ...
Article
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In this article, we analysed two millennia of historical records and environmental information to reconstruct the past distribution and examine the current distribution of snub-nosed monkeys (Rhinopithecus) in China. China. We applied trend surface analysis (TSA) to document patterns of range shifting in snub-nosed monkeys over time. Random forest was used to study the association between explanatory variables and changes in the distribution of snub-nosed monkeys over the past 2000 years. Our results showed that both the longitude and latitude of snub-nosed monkeys contracted from 0 to 2000 AD. We found that the integrated effects of human population size and changes in temperature in the Northern Hemisphere resulted in a westward and northward contraction of the snub-nosed monkey distributional range. However, the impact of fluctuating temperature was greatest during periods of low human population density (0–1200 AD), whereas from 1200 to 2000 AD, marked increases in human population size in China leading to extensive deforestation, agricultural expansion, hunting, logging and land terracing have had the greatest negative effects. Further analyses highlighted the fact that the rapid expansion of human population density in regions occupied by snub-nosed monkeys between 1700 and 2000 has resulted in the recent extirpation of this primate radiation in eastern, south-eastern and central China. We examined the interactive effects of human population growth, deforestation, agricultural expansion and climate variation on the past and current distribution of snub-nosed monkeys. Our data provide clear evidence that climate change, human population increase and human activities have differentially affected the viability and distribution of snub-nosed monkey populations over time. In particular, the marked expansion of the human population in China over the past 300 years has resulted in the extinction of Rhinopithecus populations across much of its range.
... This index gives the probability that two randomly sampled individuals in the study area will meet. It has proved especially efficient for decision making when planning connectivity improvement Girardet et al. 2013;Gurrutxaga and Saura 2013;Clauzel et al. 2015) and is the most widely used index for describing the functional efficiency of ecological networks. The PC index is computed as follows: ...
Article
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ContextLinear transportation infrastructures traverse and separate wildlife populations, potentially leading to their short- and long-term decline at local and regional scales. To attenuate such effects, we need wildlife crossings suitable for a wide range of species.Objectives We propose a method for identifying the best locations for wildlife crossings along linear infrastructures so as to improve the connectivity of species with varying degrees of mobility and living in different habitats. We evaluate highway impacts on mammal species.Methods The study area is the Grésivaudan Valley, France. We used allometric relationships to create eight virtual species and model their connectivity networks, developing a nested method defining populations by daily travel distances and connecting them by dispersal. We tested the gain in connectivity for each species produced by 100 and 600 crossing locations respectively in crossable, i.e. with crossing infrastructures, and uncrossable highway scenarios. We identified the crossings that optimize the connectivity of the maximum number of species combining the results in multivariate analyses.ResultsHighly mobile species needing a large habitat area were the most sensitive to highways. The importance of locomotive performance in structuring the graphs decreased with highway impermeability. Depending on the species, the best locations improved connectivity by 0–10 and 2–75 % respectively in the crossable and uncrossable scenarios. Compromise locations were found for seven of the eight species in both scenarios.Conclusions This method could guide planners in identifying crossing locations to increase the connectivity of different species at regional scales over the long term.
Article
Context Global habitat fragmentation is a major threat to terrestrial wildlife biodiversity, and habitat restoration is an effective method to protect biodiversity. The Rhinopithecus roxellana (R. roxellana) in Hubei Province, is a first-class key protected wild animal in China, and now the fragmentation of its habitat has seriously affected species expansion and genetic diversity. Objectives To identify the causes of habitat degradation and the location of recoverable habitat patches, improve habitat connectivity, better respond to species expansion and protect biodiversity effectively. Methods Using two level sets of environmental variables to represent the past and current habitat conditions of R. roxellana in the Shennongjia region. MaxEnt model was firstly used to quantify the suitable habitat value to two levels, and then change detection method determined the habitat degradation areas between the two levels. Finally, the important values of recoverable areas were quantified and ranked with graph theory to clarify the priority of restored patches. Results The patches affected by degraded or damaged vegetation were found, then the suitable restoration patches were mapped. At last 5 patches as the priority areas of habitat restoration were conserved. Conclusions Based on MaxEnt, change detection and connectivity analysis, targeted intervention is carried out on the habitat environment of R. roxellana in Shennongjia. As an effective conservation way, restoration of degraded or damaged habitats provides a mechanism to improve habitat connectivity. Here we show a practical method for the increasingly fragmented landscape restoration.
Article
The Colobines are a group of Afroeurasian monkeys that exhibit extraordinary behavioural and ecological diversity. With long tails and diverse colourations, they are medium-sized primates, mostly arboreal, that are found in many different habitats, from rain forests and mountain forests to mangroves and savannah. Over the last two decades, our understanding of this group of primates has increased dramatically. This volume presents a comprehensive overview of the current research on colobine populations, including the range of biological, ecological, behavioural and societal traits they exhibit. It highlights areas where our knowledge is still lacking, and outlines the current conservation status of colobine populations, exploring the threats to their survival. Bringing together international experts, this volume will aid future conservation efforts and encourage further empirical studies. It will be of interest to researchers and graduate students in primatology, biological anthropology and conservation science. Additional online resources can be found at www.cambridge.org/colobines.
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The golden snub‐nosed monkey, or golden monkey, inhabits the eastern Yangtze River. The black‐and‐white snub‐nosed monkey or Yunnan snub‐nosed monkey survives between the upper reaches of the Yangtze River and the Upper Mekong River. The bones, brains and other body parts of black‐and‐white snub‐nosed monkeys were then used to prepare medicinal remedies, which amounted to several dozen animals per year in the late 1970s and early 1980s. A spatial modeling of the ecological network of black‐and‐white snub‐nosed monkeys was then carried out in order to evaluate the degree of connectivity of its habitats and the impact of different development scenarios. Ecotourism responds to a demand for interaction with nature, while developing biodiversity conservation programs and increasing financial and educational benefits for local communities.
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Graph theory (GT) is extensively applied in the ecological network analysis. This review study aimed to examine GT in the field of ecological network analysis based on the following questions: In what areas are the articles focused?, what indexes or graph-based indicators have been thus far utilized in ecological network analysis?, and what aspects of ecological network analysis have been less considered in terms of the use of the GT indicators? To address these questions, a systematic literature review was conducted and the results showed that most of the articles in this field had been fulfilled in China, the United States, and France. This theory could have implications for more research on plants and mammals. In addition, 118 indicators were identified in the field of GT in the ecological network analysis. Among these indicators, the probability of connectivity (PC) and an integral index of connectivity (IIC) had been consistently exploited in most articles. Moreover, the results revealed the increasing trend of introducing the new indicators of GT to ecological network analysis, suggesting the applicability of GT in this context. Despite the importance of ecological network resilience, it has been less reflected from the GT perspective while it can be useful and efficient in analyzing the sustainability of ecological networks within this framework. The current trend of exploiting the GT indicators delineates three future lines of development, viz. (1) the GT use more widely in ecological network analysis, (2) emerging new and more precise indexes, and (3) new concerns mainly examining ecological network resilience.
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The development of road networks over the years has caused serious damage to biodiversity. However, few studies have explored the impact of different road grades on ecological network connectivity, especially at multiple levels and at different dispersal distances. Here, we propose an analytical framework based on the integrated graph theory and the circuit theory method, in order to model the ecological network of virtual species, to evaluate connectivity at the landscape, patch, and corridor levels, and to identify the key patches and key corridors that contribute the most to the maintenance of connectivity. The empirical analysis in this study was performed on six scenarios, which were designed by successively integrating different road grades into the landscape. On this basis, the impact of different road grades on the connectivity, key patches, and key corridors in Wuhan, China, were explored. The results showed that: (1) High-grade roads have a significant impact on landscape-patch-corridor connectivity, while medium-grade roads have a similar degree of impact on patch-level connectivity as high-grade roads do. (2) Species with long dispersal ability (25 km) are susceptible to roads at the landscape and corridor levels; species with low and medium dispersal abilities (10, 15 and 20 km) are vulnerable to roads at the patch levels. (3) The importance of key patches and the resistance of key corridors are significantly increased by the influence of roads, while their spatial distribution changes slightly. This integrated framework contributes to an evaluation of the impacts of different grades road on ecological processes, so as to better provide targeted suggestions for biodiversity conservation and transportation planning.
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Ecological Network Analysis (ENA) capability has led to develop a set of indicators. Ecological Network Indicators (ENIs) investigates a range of subject in different context “e.g. Graph theory”, which is the origin of variety of questions such as following: What is the geographical distribution of studies and their relationship with each other? On what fields these studies are focused? What graph-based index or indexes have been used in the studies of ecological networks? What are the most widely used indexes in ecological studies? Accordingly, this study is to investigate the related literature between 2014 and 2019 in the framework of graph theory. To answer the mentioned question, we conducted systematic literature review. To find as many potentially eligible articles as possible, the search was performed multiple times using diverse related keywords. We identified 456 related records. After the screening process, 114 articles were left as the basis of further analysis. The results indicate that ENA applied mainly in China, USA, France. ENIs is studied more frequently among plants and mammals. We identified about 58 ENIs. But the Probability of Connectivity (PC), Integral index of connectivity (IIC) have been consistently used in most studies. Also, these two indices are used in combination with others ENIs. The outcomes show researchers introduce new indexes every year. The increasing trend of introducing new indicators shows the usability and applicability ENIs. But so far, PC, IIC, and LCP seem to be the most credible graph-based indexes for use in ecological network research. The overall results imply that graph theory as base of ecological network is developing, presents new indicators and opening new dimensions in the study and analysis of connections and communications in ecological networks. It has adequate flexibility to answer questions that may arise in the future in the field of ecological network analysis.
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Transportation infrastructure, such as railways, roads and power lines, contribute to national and regional economic, social and cultural growth and integration. Kenya, with support from the Chinese government, is currently constructing a standard gauge railway (SGR) to support the country’s Vision 2030 development agenda. Although the actual land area affected by the SGR covers only a small proportion along the SGR corridor, a significant proportion of the area supports a wide range of ecologically fragile and important ecosystems in the country, with potential wider impacts. This study used a qualitative content analysis approach to gain an understanding and perceptions of stakeholders on the potential ecological impacts of the interactions between the SGR and the traversed ecological systems in Kenya. Three dominant themes emerged: 1) ecosystem degradation; 2) ecosystem fragmentation; and 3) ecosystem destruction. Ecosystem degradation was the most commonly cited impact at while ecosystem destruction was of the least concern and largely restricted to the physical SGR construction whereas the degradation and fragmentation have a much wider footprint. The construction and operation of the SGR degraded, fragmented and destroyed key ecosystems in the country including water towers, protected areas, community conservancies and wildlife dispersal areas. Therefore, we recommend that project proponents develop sustainable and ecologically sensitive measures to mitigate the key ecosystem impacts.
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Background Gypsum ecosystems are edaphic islands surrounded by a matrix that is inhospitable to gypsum soil plant specialists. These naturally fragmented landscapes are currently exacerbated due to man-made disturbances, jeopardising their valuable biodiversity. Concomitant action of other fragmentation drivers such as linear infrastructures may increase the already high threat to these specialists. Although some evidence suggest that gypsophytes are not evolutionary dead-ends and can respond to fragmentation by means of phenotypic plasticity, the simultaneous action of barriers to genetic flow can pose a severe hazard to their viability. Here, we evaluated the effect of a highway with heavy traffic on the genetic flow and diversity in the species Lepidium subulatum , a dominant Iberian shrubby gypsophyte. Methods We tested the possible existence of bottlenecks, and estimated the genetic diversity, gene flow and genetic structure in the remnant populations, exploring in detail the effect of a highway as a possible barrier. Results Results showed variability in genetic diversity, migrants and structure. The highway had a low impact on the species since populations can retain high levels of genetic diversity and genetic parameter, like F ST and F IS , did not seem to be affected. The presence of some level of genetic flow in both sides along the highway could explain the relatively high genetic diversity in the habitat remnants. Discussion Natural fragmentation and their exacerbation by agriculture and linear infrastructures seem to be negligible for this species and do not limit its viability. The biological features, demographic dynamics and population structures of gypsum species seem to be a valuable, adaptive pre-requisite to be a soil specialist and to maintain its competitiveness with other species in such adverse stressful conditions.
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Climate change threatens endangered species and challenges current conservation strategies. Effective conservation requires vulnerability assessments for species susceptible to climate change and adaptive strategies to mitigate threats associated with climate. In this paper, we used the Maxent to model the impacts of climate change on habitat suitability of Sichuan golden monkey Rhinopithecus roxellana. Our results showed that (i) suitable habitat for Sichuan golden monkey was predicted to decrease by 37% in 2050s under climate change; (ii) the mean elevations of suitable habitat in the 2050s was estimated to shift 160 m higher; (iii) nature reserves protect 62% of current suitable habitat and 56% of future suitable habitat; and (iv) 49% of current suitable habitat was predicted to be vulnerable to future climate change. Given these results, we proposed conservation implications to mitigate the impacts of climate change on Sichuan golden monkey, including adjusting range of national park, establishing habitat corridors, and conducting long‐term monitoring.
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Context Restoring or establishing corridors between residual forest patches is one of the most adopted strategies for the conservation of animal populations and ecosystem processes in fragmented landscapes. Objectives This study aimed to assess whether it is more effective to focus restoration actions on existing corridors or to establish habitats in other strategic areas that can create new dispersal pathways to enhance connectivity. Methods We considered a real agroecosystem in northern Italy, based our analyses on graph-theory and habitat availability metrics, and focused on the Hazel Dormouse as the target species. We compared the connectivity increase resulting from (i) the simulated restoration of existing priority corridors, i.e., those with significant presence of forest but in which restoration actions would still result in considerable connectivity gains, or (ii) the simulated plantation of 30 hedgerows along new priority pathways, i.e., those areas with no current forest cover in which habitat creation would be more beneficial for connectivity. Results Implementing new priority pathways resulted in substantially larger connectivity gains (+ 38%) than when restoration efforts were concentrated in improving already existing corridors (+ 11%). Conclusions Establishing hedgerows along new pathways allowed enhancing the complementary and functionality of the full set of landscape corridors and proved more efficient than just strengthening the areas where dispersal flows were already concentrated. We demonstrated the importance of analytical procedures able to compare the effectiveness of different management strategies for enhancing connectivity. Our approach may be applied to multiple species sensitive to fragmentation in other heterogeneous landscapes and geographical contexts.
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The aim of this study is to evaluate and mitigate the impact of a high-speed railway (HSR) line on functional connectivity for the European tree frog (Hyla arborea), an amphibian species highly sensitive to habitat fragmentation. The method consists of modeling its ecological network using graph theory before and after the implementation of the infrastructure and of evaluating changes in connectivity. This diachronic analysis helps visualize the potential impact of the HSR line and to identify areas likely to be most affected by the infrastructure.
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Habitat fragmentation is a major cause of biodiversity loss; it impedes gene flow between populations and interrupts the network of habitat patches. Populations are faced with a high risk of extinction owing to their small and isolated habitat patches. The maintenance of landscape connectivity can promote population movement between habitat patches, and this is extremely important to maintain gene flow and biological dispersal in fragmented landscapes. Using current habitat patches, the least-cost distance method and graph theory were implemented to study the habitat connectivity across the distribution of the Yunnan snub-nosed monkeys, and the optimal distance threshold of landscape functional connectivity was identified. Priority protected areas referred to as “stepping stones” were quantitatively identified based on highly connected functional components. The least-cost path was estimated to determine restoration priority areas for less connected functional components. This study had the following aims: (1) to explore new methods for identifying the optimal distance threshold, (2) to analyze the connectivity between monkey groups, and (3) to quantitatively analyze priority protected areas among monkey groups. The best resistance assignment for each habitat type was determined by a landscape genetics approach that combines the relationship between the least-cost-distance and gene flow, and reflects the promotion and impediment of the landscape matrix on species movement. The optimal threshold distance of least cost comprehensively reflected landscape features and species distribution characteristics; it incorporated the habitat area of each connected component into the monkey distribution. The priority conservation area was quantified using the landscape index. Based on the results, the optimal threshold distance of least cost was 1400 cost units. Monkey groups were mainly classified into five components that did not exceed this threshold, and the connectivity scores for monkey groups within components was Component 3 > Component 1 > Component 5 > Component 4. “Stepping-stone” patches do not exist in the Longma mountain group, resulting in a disconnect between that group and other monkey groups. This connection should first be restored. The results of this study can facilitate the protection of this and other species.
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The lithium-ion battery is widely used in the fields of portable devices and electric cars with its superior performance and promising energy storage applications. The unique one-dimensional structure formed by the graphene layer makes carbon nanotubes possess excellent mechanical, electrical, and electrochemical properties and becomes a hot material in the research of lithium-ion battery. In this paper, the applicable research progress of carbon nanotubes in lithium-ion battery is described, and its future development is put forward from its two aspects of being not only the anodic conductive reinforcing material and the cathodic energy storage material but also the electrically conductive framework material.
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The black-and-white snub-nosed monkey Rhinopithecus bieti is endemic to China, where its population is fragmented into 15 isolated groups and threatened despite efforts to protect the species. Here we analyse possible habitat connectivity between the groups reported in Yunnan, using genetic, least-cost path and Euclidean distances. We detect genetic isolation between the northern and southern groups but not among the northern groups. We show that genetic distance is better explained by human disturbance and land-cover least-cost paths than by Euclidian distance. High-quality habitats were found to be more fragmented in the southern part of the study area and interspersed with human-influenced areas unsuitable for black-and-white snub-nosed monkeys, which may explain the genetic isolation of the southern groups. Potential corridors are identified based on the least-cost path analysis, and seven sensitive areas are proposed for restoration. We recommend (1) that restoration is focused on the current range of the monkeys, with efforts to reduce human disturbance and human population pressure and increase public awareness, and (2) the development of a long-term plan for habitat restoration and corridor design in the areas between groups.
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For several decades, the sprawling of urbanisation has resulted in the loss of natural habitats and in landscape fragmentation and thus represents one of the main causes of the erosion of biodiversity. Green spaces in urban areas help maintain ecological connectivity and provide ecosystem services to citizens. The impact of urban green spaces on the conservation of biodiversity and their contribution to ecological networks in urban areas have been studied. However, little is known about the area occupied by green spaces at business sites (GSBS) or about their organisation within the urban matrix and their possible contribution to the maintenance of functional connectivity at local and regional scales. This study analysed the evolution in the dynamics and locations of business sites over the past 30 years in the Ile-de-France region. Cartographic data allowed us to identify GSBS which spanned 8700 ha and represented 8% of the urban green spaces forming the herbaceous network. Using a graph theoretic modelling approach, we quantified the potential contribution of GSBS to regional connectivity. We demonstrated that GSBS did not add to connectivity in terms of total area but rather through the density of the links that these sites shared with other green spaces or via their strategic position in the network, i.e., their capacity to serve as stepping stones. The contribution of GSBS was greatest in suburban and pericentral sectors, where most business activities have been developed in the past 30 years and land resources remain available for green space development.
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Habitat restoration is one way of reducing landscape fragmentation, which is seen as a threat to biodiversity. It consists in renovating disused or degraded habitat patches or in creating new habitat patches in suitable areas. Currently, most restoration measures draw on the local knowledge of experts for selecting the best locations. But for amphibian metapopulations like the European tree frog (Hyla arborea), the search for such locations must include regional-scale connectivity in order to maintain their viability. We set up a systematic and cumulative protocol for adding new habitat patches to a pond network. Graph modelling is used to include regional-scale connectivity as a criterion to be maximized. Successive locations are tested systematically and connectivity is compared before and after the virtual addition of each new pond. The location that increases connectivity most is identified. The results show that the priority areas identified by the model are similar to those suggested by local experts from a wildlife conservation association. The two approaches are complementary because they are applied on two different scales. The patch addition method can identify strategic areas for improving global connectivity by taking into account the regional scale. Experts’ knowledge can target the precise location within the identified area for creating new habitats based on local factors of the surrounding context. In addition, our method can be also used to prioritize locations already decided on by landscape managers. Consequently, this protocol appears to be a useful tool for guiding habitat restoration in the field.
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With accelerated deforestation and fragmentation through the tropics, assessing the impact that landscape spatial changes may have on biodiversity is paramount, as this information is required to design and implement effective management and conservation plans. Primates are expected to be particularly dependent on the landscape context; yet, our understanding on this topic is limited as the majority of primate studies are at the local scale, meaning that landscape-scale inferences are not possible. To encourage primatologists to assess the impact of landscape changes on primates, and help future studies on the topic, we describe the meaning of a “landscape perspective” and evaluate important assumptions of using such a methodological approach. We also summarize a number of important, but unanswered, questions that can be addressed using a landscape-scale study design. For example, it is still unclear if habitat loss has larger consistent negative effects on primates than habitat fragmentation per se. Furthermore, interaction effects between habitat area and other landscape effects (e.g., fragmentation) are unknown for primates. We also do not know if primates are affected by synergistic interactions among factors at the landscape scale (e.g., habitat loss and diseases, habitat loss and climate change, hunting, and land-use change), or whether landscape complexity (or landscape heterogeneity) is important for primate conservation. Testing for patterns in the responses of primates to landscape change will facilitate the development of new guidelines and principles for improving primate conservation. Am. J. Primatol. © 2014 Wiley Periodicals, Inc.
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Landscape graphs are now widely used for representing and analysing ecological networks. Although several studies have provided methodological syntheses of how to use these tools to quantify functional connectivity, it is still unclear how landscape graphs can be used for decision support in land planning. This paper outlines the different types of application that may provide relevant responses to the main questions arising in land planning about ecological networks. Three approaches are distinguished according to their objective: (1) to support prioritisation within an ecological network from a conservationist perspective; (2) to increase connectivity by identifying the best locations for adding new elements to the network, either when starting from the current state of the network or when seeking to mitigate the barrier effect engendered by a development project; (3) to assess the potential impact of a development project in terms of decreased connectivity. The computations based on connectivity metrics are explained for each of these three approaches. Then each approach is illustrated in the context of a pond network near the town of Belfort, in eastern France. The results show how the same connectivity metric used in the different approaches may serve different purposes. This emphasises the potential value of landscape graphs for the land-planning decision-support process and not just for conservation purposes (i.e. prioritisation).
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We studied the ranging pattern of the wild black-and-white snub-nosed monkeys (Rhinopithecus bieti) at Xiaochangdu, Tibet from June 2003 to March 2005. Using the map grid cell method, the group home range were 16.75 km2 in summer, 10.50 km2 in winter, and 21.25 km2 total over two years. The daily travel length (DTL) averaged 765 m with a range of 350–3500 m. The results showed that DTL in winter was significantly shorter than those of in summer and spring. Temperature, rainfall, food availability, and human disturbance correlated positively with DTL. According to the maximum observed group size and estimated total home range, population density and biomass of R. bieti were 9.1 individuals/km2 and 88.6 kg/km2, respectively. The temporal and spatial variations of food resources and patterns of human disturbance largely determine the ranging behavior of R. bieti at Xiaochangdu.
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The destruction and fragmentation of habitats due to anthropogenic land use changes have led to the decline of numerous species by reducing the size and the connectivity of the remaining local populations and so contributing to their isolation. The impact of habitat fragmentation can be modeled using landscape graphs, which have become a popular tool. Habitat reduction and fragmentation has been suggested as one hypothesis for the decline of the lesser horseshoe bat Rhinolophus hipposideros in most of western and central Europe. Consequently, we expected habitat connectivity to influence the spatial distribution of the species, particularly through the presence of maternity roosts, which are essential for the persistence of the species. We designed this study to evaluate the impact of landscape connectivity on the distribution of the lesser horseshoe bat by comparing the predictive power of landscape composition alone with a model including both landscape composition and connectivity. We assessed the impact of landscape composition on maternity roost presence for different distances covered daily by bats (600, 2500 and 5000 m). We then applied a landscape graph-based approach to the roosting habitat of the lesser horseshoe bat to extract several patch-level metrics representing the functional connectivity of the landscape at different spatial scales. The results from those approaches show that the bats’ presence in the Franche-Comté region depends on the availability of wooded elements near small built areas and, at a broader scale, on the spatial integration of maternity roosts into a connected network allowing exchanges of individuals among roosts. This approach is a promising way to establish whether the presence probability of a given species depends on the potential connectivity between habitat patches quantified at different spatial scales. We expect that this method can be applied to taxa for which habitat fragmentation is one of the causes of population decline. We anticipate that using a graph-based species distribution model as a tool to predict species presence may focus conservation efforts on areas where habitat potential connectivity and landscape composition together should be taken into account, e.g. where anthropogenic landscape modifications are the main drivers of habitat connectivity..
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This paper addresses the relationship between anthropogenic forest habitat fragmentation and the form of urban patterns. Using a two-step methodology we first generate 40 theoretical residential development scenarios following a repeatable procedure; the simulated urban forms are either moderately compact or fractal. Then, we compare the scenarios according to the functional connectivity of the remaining forest habitat using a graph-based approach. The methodology is applied to the urban region of Besanc¸ on (France), where forest surfaces are considered as a generic habitat for several animal species. Results obtained show that fractal scenarios of residential development are almost equivalent to moderately compact scenarios regarding the connectivity of forest habitat when the residential development is weak. In the case of a more intense residential development, fractal scenarios are superior to nonfractal scenarios when low dispersal distances of animals are concerned.
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Species distribution models (SDMs) are commonly used in ecology to map the probability of species occurrence on the basis of predictive factors describing the physical environment. We propose an improvement on SDMs by using graph methods to quantify landscape connectivity. After (1) mapping the habitat suitable for a given species, this approach consists in (2) building a landscape graph, (3) computing patch-based connectivity metrics, (4) extrapolating the values of those metrics to any point of space, and (5) integrating those connectivity metrics into a predictive model of presence. For a given species, this method can be used to interpret the significance of the metrics in the models in terms of population structure. The method is illustrated here by the construction of an SDM for the European tree frog in the region of Franche-Comte' (France). The results show that the connectivity metrics improve the explanatory power of the SDM and emphasize the important role of the habitat network
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Landscape connectivity is crucial for many ecological processes, including dispersal, gene flow, demographic rescue, and movement in response to climate change. As a result, governmental and non-governmental organizations are focusing efforts to map and conserve areas that facilitate movement to maintain population connectivity and promote climate adaptation. In contrast, little focus has been placed on identifying barriers-landscape features which impede movement between ecologically important areas-where restoration could most improve connectivity. Yet knowing where barriers most strongly reduce connectivity can complement traditional analyses aimed at mapping best movement routes. We introduce a novel method to detect important barriers and provide example applications. Our method uses GIS neighborhood analyses in conjunction with effective distance analyses to detect barriers that, if removed, would significantly improve connectivity. Applicable in least-cost, circuit-theoretic, and simulation modeling frameworks, the method detects both complete (impermeable) barriers and those that impede but do not completely block movement. Barrier mapping complements corridor mapping by broadening the range of connectivity conservation alternatives available to practitioners. The method can help practitioners move beyond maintaining currently important areas to restoring and enhancing connectivity through active barrier removal. It can inform decisions on trade-offs between restoration and protection; for example, purchasing an intact corridor may be substantially more costly than restoring a barrier that blocks an alternative corridor. And it extends the concept of centrality to barriers, highlighting areas that most diminish connectivity across broad networks. Identifying which modeled barriers have the greatest impact can also help prioritize error checking of land cover data and collection of field data to improve connectivity maps. Barrier detection provides a different way to view the landscape, broadening thinking about connectivity and fragmentation while increasing conservation options.
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Temperate forests are characterized by pronounced climatic and phenological seasonality. Primates inhabiting such environments experience prolonged resource scarcity and low ambient temperatures in winter and are expected to adjust time allocation and foraging behavior so as to maintain their energy balance. We analyzed the activity scheduling of a group of Yunnan snub-nosed monkeys (Rhinopithecus bieti) based on data collected over 20 months in the high-altitude (>3000 m) Samage Forest, Baimaxueshan Nature Reserve, PRC. The forest consists of evergreen conifers and oaks and deciduous broadleaf trees. The diet varied seasonally, with young leaves preferentially exploited in spring and fruits in summer. The monkeys subsisted on readily available fallback resources (mainly lichens) in winter [Grueter et al. in (Am J Phys Anthropol 140:700-715, 2009)]. We predicted that this switch to a relatively low-quality diet would prompt an increase in feeding effort and decrease in moving effort. We found that the monkeys spent significantly more time feeding in winter than in the other seasons. The monthly time devoted to feeding was also negatively correlated with temperature and positively with percentage of lichens in the diet. Time spent on moving did not vary among seasons or with temperature, but day-journey length was found to be longer on hotter days. Time spent resting was lower in winter and under colder conditions and was also negatively correlated with time spent feeding, indicating that resting time is converted into feeding time during times of ecological stress. These results indicate a strong effect of seasonality on time allocation patterns, constraints on inactivity phases, and the prevalence of an energy-conserving foraging strategy in winter, when costs of thermoregulation were high and the availability of preferred food was low.
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Roads are a widespread and increasing feature of most landscapes. We reviewed the scientific literature on the ecological effects of roads and found support for the general conclusion that they are associated with negative effects on biotic integrity in both terrestrial and aquatic ecosystems. Roads of all kinds have seven general effects: mortality from road construction, mortality from collision with vehicles, modification of animal behavior, alteration of the physical environment, alteration of the chemical environment, spread of exotics, and increased use of areas by humans. Road construction kills sessile and slow-moving organisms, injures organisms adjacent to a road, and alters physical conditions beneath a road. Vehicle collisions affect the demography of many species, both vertebrates and invertebrates; mitigation measures to reduce roadkill have been only partly successful. Roads alter animal behavior by causing changes in home ranges, movement, reproductive success, escape response, and physiological state. Roads change soil density, temperature, soil water content, light levels, dust, surface waters, patterns of runoff, and sedimentation, as well as adding heavy metals (especially lead), salts, organic molecules, ozone, and nutrients to roadside environments. Roads promote the dispersal of exotic species by altering habitats, stressing native species, and providing movement corridors. Roads also promote increased hunting, fishing, passive harassment of animals, and landscape modifications. Not all species and ecosystems are equally affected by roads, but overall the presence of roads is highly correlated with changes in species composition, population sizes, and hydrologic and geomorphic processes that shape aquatic and riparian systems. More experimental research is needed to complement post-hoc correlative studies. Our review underscores the importance to conservation of avoiding construction of new roads in roadless or sparsely roaded areas and of removal or restoration of existing roads to benefit both terrestrial and aquatic biota. Resumen: Las carreteras son una característica predominante y en incremento de la mayoría de los paisajes. Revisamos la literatura científica sobre los efectos ecológicos de las carreteras y encontramos sustento para la conclusión general de que las carreteras están asociadas con efectos negativos en la integridad biótica tanto de ecosistemas terrestres como acuáticos. Las carreteras de cualquier tipo ocasionan siete efectos generales: mortalidad ocasionada por la construcción de la carretera; mortalidad debida a la colisión con vehículos; modificaciones en la conducta animal; alteración del ambiente físico; alteración del ambiente químico; dispersión de especies exóticas e incremento en el uso de áreas por humanos. La construcción de carreteras elimina a organismos sésiles y a organismos de lento movimiento, lesiona a organismos adyacentes a la carretera y altera las condiciones físicas debajo ella misma. Las colisiones con vehículos afectan la demografía de muchas especies tanto de vertebrados como invertebrados; las medidas de mitigación para reducir la pérdida de animales por colisiones con vehículos han sido exitosas solo de manera parcial. Las carreteras alteran la conducta animal al ocasionar cambios en el rango de hogar, movimientos, éxito reproductivo, respuesta de escape y estado fisiológico. Las carreteras cambian la densidad del suelo, temperatura, contenido de agua en el suelo, niveles de luz, polvo, aguas superficiales, patrones de escurrimiento y sedimentación, además de agregar metales pesados (especialmente plomo), sales, moléculas orgánicas, ozono y mutrientes a los ambientes que atraviesan. Las carreteras promueven la dispersión de especies exóticas al alterar los hábitats, al estresar a las especies nativas y proveer corredores para movimiento. Las carreteras también promueven el incremento de la caza y la pesca, el hostigamiento pasivo de animales y modificaciones del paisaje. No todas las especies ni todos los ecosistemas son afectados por las carreteras de igual forma, pero en general la presencia de carreteras está altamente correlacionada con cambios en la composición de especies, los tamaños poblacionales y los procesos hidrológicos y geomorfológicos que afectan a la estructura de sistemas acuáticos y reparios. Se necesita más investigación experimental para complementar estudios correlativos post-hoc. Nuestra revisión hace énfasis en que en trabajos de conservación es importante evitar la construcción de nuevas carreteras en áreas carentes de ellas o en áreas con pocas carreteras, además de remover o restaurar carreteras existentes con la finalidad de beneficiar tanto a la biota acuática como la terrestre.
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There are few data on the daily ranging distances of Yunnan snub-nosed monkeys (Rhinopithecus bieti). We fitted 1 adult male from a natural group at Jinsichang in China’s Yunnan Province with a global positioning system (GPS) collar and tracked him from December 2003 to October 2004 to estimate the daily ranging distances of the group. The total acquisition rate of the GPS collar was 82.2%, which indicates that one can use GPS collars to track the species efficiently in high-altitude, temperate, coniferous forest. We obtained group locations or fixes at 5 predetermined times during the day. The sleeping sites of the subjects are the key points to estimate the day range. We compared 2 measures of day range: the 2-point straight-line displacement and the multipoint cumulative daily ranging distance. Straight-line displacement between 2 consecutive mornings or 2 consecutive evenings can substitute for that between the morning sleeping site and the evening sleeping site. In general, the group does not move at night. The 2 measures of day range yielded different results. The multipoint cumulative daily ranging distance was the method of choice to measure their daily travel costs. The minimum required number of fixes per day was 3. Per statistical evidence, the number of full-day group follows per month influences the estimate of day range of the group and ≥10 d is required to obtain a reliable estimate; 5 d per month might not be enough. We dealt mainly with the methodologic aspects of day range calculations. We did not address functional aspects on the estimate of day range, viz. the influence of vegetation, food distribution patterns, climate change, seasonality, and the monkey group itself.
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One of the biggest threats to the survival of many plant and animal species is the destruction or fragmentation of their natural habitats. The conservation of landscape connections, where animals, plants, and ecological processes can move freely from one habitat to another, is therefore an essential part of any new conservation or environmental protection plan. In practice, however, maintaining, creating, and protecting connectivity in our increasingly dissected world is a daunting challenge. This fascinating volume provides a synthesis on the current status and literature of connectivity conservation research and implementation. It shows the challenges involved in applying existing knowledge to real-world examples and highlights areas in need of further study. Containing contributions from leading scientists and practitioners, this topical and thought-provoking volume will be essential reading for graduate students, researchers, and practitioners working in conservation biology and natural resource management.
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One of the biggest threats to the survival of many plant and animal species is the destruction or fragmentation of their natural habitats. The conservation of landscape connections, where animals, plants, and ecological processes can move freely from one habitat to another, is therefore an essential part of any new conservation or environmental protection plan. In practice, however, maintaining, creating, and protecting connectivity in our increasingly dissected world is a daunting challenge. This fascinating volume provides a synthesis on the current status and literature of connectivity conservation research and implementation. It shows the challenges involved in applying existing knowledge to real-world examples and highlights areas in need of further study. Containing contributions from leading scientists and practitioners, this topical and thought-provoking volume will be essential reading for graduate students, researchers, and practitioners working in conservation biology and natural resource management.
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The maintenance of habitat connectivity is promoted as a method of biodiversity conservation in forest management. Graph based metrics have demonstrated efficacy at deriving landscape scale connectivity metrics from habitat maps. The response of a graph-based connectivity metric to changes in the size of gaps considered to fragment habitat is proposed as a method of quantifying the impacts of changes in landscape composition on connectivity across a range of spatial scales. The parameters that describe this relationship are proposed as indices to quantify changes in the amount, fragmentation and spatial dispersion of habitat in a landscape. Systematic manipulations of landscape structure demonstrated response curve sensitivity to the impacts of forestry that are predicted by the literature to affect habitat connectivity. The response to controlled manipulations of landscape structure was used to guide an examination of the efficacy of distributing habitat reserves as corridors to mitigate the impacts of forestry on landscape connectivity. I conclude that the parameters that describe the relationship between spatial scale and the probability of connectivity index values can be used to compare the impacts of alternative forest management strategies on landscape connectivity, distributing conservation areas as corridors resulted in minimal benefits to landscape connectivity, and that the benefits of corridors were further reduced when natural disturbances were included in model simulations.
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Human disturbances contribute significantly to the decrease in the quantity and connectivity of the natural habitats. Taking Lincang City in Lancang River Valley as a case study, we focused on the forest fragmentation and habitat connectivity loss associated with its road network and expansion in the past 15 years. Our findings show that, from 1991 to 2006, its forest habitat (>25 ha) decreased to 18.3% of the total area due to fragmentation. Landscape fragmentation indices (NP, PLAND, and LPI) changed more than the landscape shapes and the aggregation indices (SHAPE, FRAC, and DIVISION). Habitat loss occurred more often in the lower elevations and in areas near the city and road network. Landscape connectivity loss was 91.3%, which showed a more significant decrease than did the landscape pattern changes. With sensitivity analysis of different animals’ dispersal abilities and landscape resistance consideration, our study reveals that landscape connectivity could be more effective in showing the potential ecological effects caused by city and road network extension.
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1. Climate and land-use changes will require species to move large distances following shifts in their suitable habitats, which will frequently involve traversing intensively human-modified landscapes. Practitioners will therefore need to evaluate and act to enhance the degree to which habitat patches scattered throughout the landscape may function as stepping stones facilitating dispersal among otherwise isolated habitat areas. 2. We formulate a new generalized network model of habitat connectivity that accounts for the number of dispersing individuals and for long-distance dispersal processes across generations. By doing so, we bridge the gap between complex dynamic population models, which are generally too data demanding and hence difficult to apply in practical wide-scale decision-making, and simpler static connectivity models that only consider the amount of habitat that can be reached by a single average disperser during its life span. 3. We find that the loss of intermediate and sufficiently large stepping-stone habitat patches can cause a sharp decline in the distance that can be traversed by species (critical spatial thresholds) that cannot be effectively compensated by other factors previously regarded as crucial for long-distance dispersal (fat-tailed dispersal kernels, source population size). 4. We corroborate our findings by showing that our model largely outperforms previous connectivity models in explaining the large-scale range expansion of a forest bird species, the Black Woodpecker Dryocopus martius, over a 20-year period. 5. The capacity of species to exploit the opportunities created by networks of stepping-stone patches largely depends on species-specific life-history traits, suggesting that species assemblages traversing fragmented landscapes may be exposed to a spatial filtering process driving long-term changes in community composition. 6. Synthesis and applications. Previous static connectivity models seriously underestimate the importance of stepping-stone patches in sustaining rare but crucial dispersal events. We provide a conceptually broader model that shows that stepping stones (i) must be of sufficient size to be of conservation value, (ii) are particularly crucial for the spread of species (either native or invasive) or genotypes over long distances and (iii) can effectively reduce the isolation of the largest habitat blocks in reserves, therefore largely contributing to species persistence across wide spatial and temporal scales.
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Abstract As long linear features on the landscape, railways, roads and highways have impacts on wildlife and wildlife habitat that are disproportionateto the area of land that they occupy. In addition to
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Recent years have shown a rapid increase in the number of published studies that advocate network analysis (graph theory) to ecologically manage landscapes that suffer from fragmentation and loss of connectivity. This paper studies the reasons, benefits and difficulties of using network analysis to manage landscape fragmentation in the practice of land-use planning. The results are based on interviews with thirteen municipal ecologists and environmental planners in Stockholm, Sweden, who had been introduced to a GIS-tool for network-based connectivity analysis. Our results indicate that fragmentation is not considered enough in municipal planning and demonstrate that none of the interviewed practitioners used systematic methods to assess landscape connectivity. The practitioners anticipate that network-level and patch-level connectivity measures and maps would help them to communicate the meaning and implications of connectivity to other actors in the planning process, and to better assess the importance of certain habitats affected by detailed plans. The main difficulties of implementing network-based connectivity analyses reported by the respondents related to the choice of focal species and the lack of model input in terms of landscape data and dispersal distances. The main strengths were expressed by the practitioners as graphical, quantitative and credible results; the ability to compare planning alternatives and to find critical sites in a more objective manner than today; and to relate local planning and ecology to the regional structure of the landscape. Many respondents stressed the role of fragmentation assessments in the endeavor to overcome current spatial mismatches of ecological and administrative scales.